(a) Field of the Invention
The present invention is directed to to a positive active material for a rechargeable lithium battery and, more particularly, to a positive active material for a rechargeable lithium battery exhibiting high capacity.
(b) Description of the Related Art
As the recent trend is toward more compact and lighter portable electronic equipment, the need has increased for a high performance and high capacity battery for electric power for portable electronic equipment. Especially with the forthcoming commercialization of IMT 2000 service, the demand for high capacity battery is greater than ever, and many battery manufacturers are already intensely researching high specific capacity batteries.
In order to increase the specific capacity of a battery, either development of a high capacity positive active material or a more compact positive active material content is needed.
For a high-capacity positive active material, LiCoO2 is widely used, and there is considerable desire to find a higher energy-density active material. One scheme to satisfy such a demand is to develop LiNixCoyO2 (where, x=0.1 to 0.99, and y=0.01 to 0.9) or LiNixMnyO2 (where, x=0.1 to 0.99, and y=0.01 to 0.9) compounds for the positive active material, which exhibit a higher discharge capacity than LiCoO2 by 20-30%. Another scheme is to increase the energy density per weight of the positive active material by using a nano composite compound of V or Fe.
In order to increase the loading level of the positive active material in the given volume of the battery cell, a thin separator or a thin can may be used. Alternatively, the density of the active composite of the electrode can be increased to improve the volumetric energy density (Wh/Liter) of the battery cell.
Although many advances have been made in the technology of positive active materials for batteries, the desire to further improve the charging and discharging capacity of the active materials led to continuous development of such materials.